Circuit breaker construction

ABSTRACT

A CIRCUIT BREAKER HAVING A BIMETAL CONDUCTOR NORMALLY IN BRIDGING ENGAGEMENT WITH TWO SPACED CONTACTS AND BEING RESPONSIVE TO THE PRESENCE OF A CURRENT THEREIN IN EXCESS OF A PREDETERMINED VALUE TO MOVE OUT OF BRIDGING ENGAGEMENT WITH THE CONTACTS, THE CONDUCTOR INCORPORATING SPRING MEANS ENABLING SUCH MOVEMENT OF THE CONDUCTOR AND RESTRAINING RETURN MOVEMENT OF THE CONDUCTOR BRIDGING ENGAGEMENT WITH THE CONTACTS. A MANIPULATABLE RESET MEMBER IS PROVIDED TO RESTORE THE BIMETAL CONDUCTOR TO ITS NORMAL POSITION AND INCORPORATES APPARATUS FOR PREVENTING BRIDGING ENGAGEMENT BETWEEN THE CONDUCTOR AND THE CONTACTS UNTIL SUCH TIME AS THE RESET MEMBER DISENGAGES THE CONDUCTOR.

1971 M. w. IPOLKINGHORN 3,555,479

C IRCUIT BREAKER CONSTRUCT I ON Filed Sept. 8, 19s? INVENTOR MELVIN W. POLKINGHORN US. Cl. 337-91 16 Claims ABSTRACT OF THE DISCLOSURE A circuit breaker having a bimetal conductor normally in bridging engagement with two spaced contacts and being responsive to the presence of a current therein in excess of a predetermined value to move out of bridging engagement with the contacts, the conductor incorporating spring means enabling such movement of the conductor and restraining return movement of the conductor into bridging engagement with the contacts. A manipulatable reset member is provided to restore the bimetal conductor to its normal position and incorporates apparatus for preventing bridging engagement between the conductor and the contacts until such time as the reset member disengages the conductor.

The invention disclosed herein relates to a circuit breaker construction of the kind having a bimetal conductive strip which normally bridges a pair of terminals and which is automatically operable in response to a current in excess of a predetermined value to break the circuit to the terminals. More particularly, the invention pertains to a circuit breaker construction having an improved bimetal conductor which precludes its return movement to circuit making position and including manually operable reset means for restoring the conductor to its circuit making position without subjecting the engageble and disengageable contacts to arcing and without subjecting the operator to any possibility of electrical shock.

Many kinds of circuit breakers have been proposed heretofore. Some of the known circuit breakers are entirely automatic in that they interrupt a circuit when the current exceeds a predetermined value and return to circuit making condition shortly after interruption of the circuit. Others are semiautomatic in operation in that they function automatically to interrupt the circuit, but must be reset manually. The semiautomatic circuit breakers usually incorporate delicate and sometimes expensive devices for preventing automatic resetting of the circuit breakers and, so far as is known, restoration of the circuit breakers to its operative condition is efiected while some part of the body of the switch operator is in contact with some part of the switch. Such a construction is objectionable for the reason that it subjects the switch operator to the risk of injury.

Some of the known circuit breakers make use of a snapacting bimetal strip which normally engages a fixed contact and away from which the bimetal strip moves as it becomes overheated. At a point in time just prior to the snap action of the bimetal strip the engagement pressure between the strip and the fixed contact is minimal, thereby subjecting the contacts to the possibility of chatter and arcing.

An object of this invention is to provide a semiautomatic circuit breaker which overcomes or greatly minimizes the aforementioned objections.

Another object of the invention is to provide a circuit breaker construction having a thermally responsive circuit making and breaking conductor provided with self-con- United States Patent 3,555,479 Patented Jan. 12, 1971 icetained means for resisting its return to circuit making position following its movement to circuit breaking position.

A further object of the invention is to provide a semiautomatic circuit breaker in which the parts are small in number and easily and quickly assembled, thereby minimizing the cost of manufacture.

Another object of the invention is to provide a semiautomatic circuit breaker construction in which resetting of the circuit making and breaking conductor to its circuit making position cannot be eflected until the body of the switch operator is in a safe position with respect to the current conducting parts of the circuit breaker.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings, in which:

FIG. 1 is an elevational view, on a reduced scale of a circuit breaker constructed in accordance with the invention;

FIG. 2 is a transverse sectional view, on an enlarged scale, of the apparatus shown in FIG. 1, but rotated through and illustrating the conductive parts in circuit making positions;

FIG. 3 is a view similar to FIG. 2, but illustrating the conductive parts in circuit breaking positions;

FIG. 4 is a view similar to FIG. 3, and illustrating the initial phase of resetting of the conductive parts to their circuit making positions; and

FIG. 5 is a sectional view taken on the line 55 of FIG. 2.

The apparatus comprises a substantially cup-shaped casing or housing 1 formed of any suitable insulating material and having a base wall 2 from which extend upstanding side andend walls 3 and 4, respectively. Secured to the end walls by means of lugs 6 is a preferably metal cover plate 5. Mounted in the casing base 2 is a pair of electrically conductive terminals 7 and 8 which are secured in openings formed in the base 2 by means of bent over tangs 9 and 10, respectively. Fixed to the terminal 7 within the casing is one end of a resilient contact blade 11, the opposite end of which is free. Between the ends of the blade is a leg 12 terminating in a laterally extending foot 13 around which is positioned a rubber or other electrically insulating sleeve 14. The terminal 8 includes a relatively stiff, conductive leg 15 which extends inwardly of the casing 1 and is provided with a slot 16 adjacent its free end.

A circuit making and breaking conductor member 17 comprises an elongated, substantially flat member 18 composed of two dissimilar, electrically conductive strips of metal secured back to back. One end of the member 18 is provided with a longitudinally projecting tang 19 which is fitted into the slot 16 in the terminal arm 15. The opposite end of the member 18 terminates in a spadeor wedgeshaped nose 20 that is accommodated in an opening 21 formed in the end wall 4 of the casing. The members 4 and 15, therefore, constitute the means, for mounting the conductor 17, but the distance between the members 4 and 15 is less than the overall length of the member 18. Consequently, the member 18 assumes a bowed configuration when it is assembled with its associated parts.

The assembly of the conductor 17 within the casing is such that the member 18 is interposed between the contact blade 11 and the foot 13 so as to position a silver or other conductive button 22 carried by the member .18 adjacent the free end of the blade 11. In its normal or circuit making position the member 18 is bowed in a direction toward the base wall 2 so as to bridge and electrically connect the conductive terminal parts 11 and 15. In these positions of the parts the blade 11 is stressed somewhat by its engagement with the conductor 18 so 7 3 as to assure good electrical contact between the parts 11 and 22.

An important characteristic of the conductor 17 is that it incorporates self-contained, conductive s ring means 23 which enables the overall length of the conductor to be varied. In the disclosed embodiment of the invention the spring 23 comprises a substantially U-shaped bend or loop 23A in the member 18 which is located between the ends of the member and preferably closer to the mounting member 15 than to the mounting wall 4. The purpose and function of the spring means 23 will be pointed out hereinafter.

Although the conductive member 18 normally is bowed in a direction toward the base wall 2, it may be bowed in the opposite direction, as is shown in FIG. 3. In this position of the member 18 the contacts 11 and 22 are disengaged, and the disengagement of those contacts enables the resilience of the contact 11 to position the latter at a somewhat steeper incline inwardly of the easmg.

Reciprocable reset means 24 is provided to return the member 18 from the position shown in FIG. 3 to the position shown in FIG. 2 and comprises a plunger 25 formed of insulating material mounted in a tubular boss 26 formed in the cover plate 5. The inner end of the plunger 25 terminates in a head 27 that is spaced from the shank of the plunger 25 by a reduced neck 28. The plunger 25 is constantly biased to the outwardly projected position shown in FIGS. 2 and 3 by a leaf spring 29, one end of which is welded or otherwise suitably fixed as at 30 to the inner surface of the 'wall and the other end of which is slotted as at 31 to accommodate the plunger neck 28. Between its opposite ends, the spring 29 is provided with an offset operating part 32 that is adapted to engage the foot 13 of the contact 11.

To condition the apparatus for operation, the casing 1 is supported in any convenient location and the terminals 7 and 8 connected in an electric circuit. In its normal position the conductor 17 is stable and is bowed toward the base wall 2 so as to bridge and electrically connect the terminals 7 and 8 to complete a circuit therebetween. The conductor 17 is maintained in its circuit making position by the action of two separate and distinct forces: first, the bowing force exerted on the member 18 because of its being of greater length than the spacing between its two supporting members 4 and 15 and second, the resistance to deformation of the spring loop 23. In this connection, it should be observed that the thickness ofthe bimetal member 18 is less than the thickness of the terminal leg 15, thereby enabling the spring 23 to yield prior to yielding of the leg 15.

When an electric. current is caused to pass between the terminals 7 and 8 via the conductor 17, the presence of current in the conductor in excess of a predetermined value will cause unequal heating of the dissimilar metal strips, resulting in suflicient force being applied on the member .18 as to cause it to be deflected from the circuit making position shown in FIG. 2 toward the circuit breaking position shown in FIG. 3 in which the contacts 11 and 22 are spaced from one another.

As the member 18 moves from the position shown in FIG. 1 toward an intermediate position, the resilience of the spring blade 11 will cause the latter to follow the member, thereby maintaining good electrical contact between the parts 11 and 22, and incidentally effecting a wiping action between them. As the member 18 deflects, the spring 23 is bowed or collapsed as the member moves toward a nonbowed or planar condition. As soon as the member 18 passes through the planar condition, the resilience of the spring 23 and of the member itself will snap the member 18 to the bowed condition shown in FIG. 3 in which the current path is broken. As soon as the circuit is broken, current no longer will pass through the member 18, whereupon the dissimilar metal strips will cool. Upon cooling of the metal strips, the member 18 will have a natural tendency to resume its unbowed condition, but the bowing force exerted on the conductor by the mounting devices 4 and 15, coupled with the resistance of the spring 23 to deformation, is suflicient to maintain the member 18 in its bowed, circuit breaking position. The conductor 17, therefore, is stable in its open circuit position and is not capable of returning automatically to its circuit making position.

When the condition resulting in the excessive current is remedied, the conductor 17 may be restored to its circuit making position by an operators depressing the reset plunger 25, as is indicated in FIG. 4. As the plunger is depressed, the spring 29 simultaneously is displaced. The length of the leg 12 is such that the operating portion 32 of the spring will engage the foot element 13 prior to the engagement of the plunger head 27 with the conductive member 18. Thus, as the plunger is depressed the contact blade 11 is displaced prior to deflection of the member 18 so as to prevent engagement between the contacts 11 and 22 until such time as the plunger 25 is released by the operator. When the plunger is released, the spring 29 will restore the latter to its projected position and disengage the foot 13, whereupon the contacts 11 and 22 may engage one another and reestablish a circuit between the terminals 7 and 8. Consequently, no part of the operators body need engage any part of the circuit breaker at the time the circuit is reestablished.

The disclosed embodiment is representative of a presently preferred form of the invention, but is intended to be illustrative rather than definitive thereof. The invention is defined in the claims.

I claim:

1. A circuit breaker construction comprising spaced apart terminal means; thermally sensitive, flexible means; means mounting said flexible means for deflection in response to a predetermined change in temperature of said flexible means from a first stable position effecting electrical connection of said terminal means to a second stable position effecting electrical disconnection of said terminal means; and yieldable means integral with and between the ends of said flexible means acting on the latter in each of said positions to restrain deflection of said flexible means from either of said positions to the other, said yieldable means being operable to prevent deflection of said flexible means from said second position to said first position in the absence of the application of an external deflecting force to said flexible member.

2. The construction set forth in claim 1 including manipulatable means; and means mounting said manipulatable means for movement into engagement with said flexible means for applying to the latter an external force of such magnitude as to overcome said yieldable means and deflect said flexible means from said second position to said first position.

3. The construction set forth in claim 1 wherein said mounting means comprises spaced supports and wherein said flexible means is supported at its opposite ends by said supports.

4. The construction set forth in claim 3 wherein the length of said flexible means is greater than the spacing between said supports.

5. The construction set forth in claim 1 wherein said part of said flexible means is a substantially U-shaped loop formed in said flexible means.

6. The construction set forth in claim 1 wherein said yieldable means includes said mounting means.

7. The construction set forth in claim 6 wherein said mounting means comprises at least one resilient member.

8. The construction set forth in claim 1 wherein said flexible means is electrically conductive and wherein the temperature of said flexible means is affected by current flowing therein.

9. The construction set forth in claim 1 wherein said flexible means is bi-metallic.

10. A circuit breaker construction comprising spaced terminal means at least one of which is resilient; a thermally responsive, flexible conductor deflectable from a first stable position to a second stable position in response to a current therein in excess of a predetermined value; means mounting said conductor for bridging engagement with said terminal means when said conductor is in its first position; yieldable means acting on said conductor and forming a conductive part of the latter for restraining deflection of said conductor from either of said positions to the other; manipulatable means; means mounting said manipulatable means for movements toward and away from said conductor and operable to restore the latter to its first position; and means responsive to movement of said manipulatable means toward said conductor to displace said resilient conductive member and prevent bridging engagement between said conductor and said terminal means.

11. The construction set forth in claim 10 including spring means acting on said manipulatable means and biasing the latter away from said conductor.

12. The construction set forth in claim 11 wherein the means for displacing said resilient conductive member is carried by said spring means.

13. A circuit breaker construction comprising a casing; a pair of spaced apart terminals carried by said casing; an elongated, flexible, bi-metal conductor; means mounting said conductor in a bowed position such that it has a first stable position in bridging engagement with said termianls, said conductor being deflectable in response to a current therein in excess of a predetermined value to a second stable, bowed position out of bridging engagement with said terminals; spring means incorporated in said conductor for yieldably resisting movement of the latter from either of said positions to the other; reset 3 6 means operable in response to movement of said reset means toward said conductor to displace said resilient contact and prevent engagement of the latter by said conductor.

14. The construction set forth in claim 13 wherein said conductor is supported at its opposite ends by said mounting means and wherein said conductor has an unbowe'd length greater than the distance between said mounting means.

15. The construction set forth in claim 13 wherein yieldable means acting on said reset means and biasing the latter in a direction away from said conductor.

16. The construction set forth in claim 13 wherein said operating means forms a part of said reset means.

References Cited UNITED STATES PATENTS 1,973,800 9/1934 Curtis 20067D2 2,413,130 12/1946 Aitken 200-67(D2) 2,467,745 4/1949 Harrison 33789 2,948,787 8/1960 Frey et al 33791 3,187,145 6/1965 Grabinski 33791 3,331,934 7/1967 Brackett 33791 2,363,376 11/1944 Woodman 337 379 3,057,982 10/1962 Grover et a1 337343 2,508,637 5/1950 Bolesky 337-91 2,469,217 5/1949 rSway 337365 1,992,047 2/1935 Spencer 337343(X) 2,405,767 8/1946 Sprague 337-366(X) FOREIGN PATENTS 467,652 8/1950 Canada 337-91 965,420 6/1957 Germany 337380 BERNARD A. GILHEANY, Primary Examiner D. M. MORGAN, Assistant Examiner US. Cl. X.R. 

